Nemoto Takayuki K, Fukuma Yutaka, Itoh Hideaki, Takagi Takashi, Ono Toshio
Division of Oral Molecular Biology, Department of Developmental and Reconstructive Medicine, Course of Medical and Dental Sciences, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8588.
J Biochem. 2006 Apr;139(4):677-87. doi: 10.1093/jb/mvj071.
The 70-kDa heat shock protein (Hsp70) is predominantly present intracellularly as a monomer, but a small population is converted to dimers and oligomers under certain conditions. In the present study, we investigated the dimeric structure of human inducible Hsp70. As reported earlier, the C-terminal client-binding domain (amino acids 382-641) was required for the dimerization. A 40-amino acid deletion in the client-binding domain from either the N-terminus or C-terminus greatly enhanced the dimerization potential of Hsp70. Limited proteolysis indicated that the dimer formed through truncation from the C-terminus had a conformation similar to that of the non-truncated form. Truncation experiments demonstrated that the client-binding sub-domain (amino acids 382-520) with its adjacent region up to amino acid 541 was not sufficient for the dimerization but that the region up to amino acid 561 was sufficient. Interestingly, the dimer formed through truncation from the C-terminus acquired a homomeric disulfide bridge at Cys574.
70 kDa热休克蛋白（Hsp70）在细胞内主要以单体形式存在，但在某些条件下，一小部分会转化为二聚体和寡聚体。在本研究中，我们研究了人诱导型Hsp70的二聚体结构。如先前报道，二聚化需要C端客户结合结构域（氨基酸382 - 641）。从N端或C端对客户结合结构域进行40个氨基酸的缺失极大地增强了Hsp70的二聚化潜力。有限蛋白酶解表明，从C端截断形成的二聚体具有与未截断形式相似的构象。截断实验表明，客户结合亚结构域（氨基酸382 - 520）及其直至氨基酸541的相邻区域不足以实现二聚化，但直至氨基酸561的区域是足够的。有趣的是，从C端截断形成的二聚体在Cys574处获得了一个同源二硫键。
